Reactor and process for upgrading heavy hydrocarbon oils

ABSTRACT

A reactor for conducting a process using supercritical water to upgrade a heavy hydrocarbon feedstock into an upgraded hydrocarbon product or syncrude with highly desirable properties (low sulfur content, low metals content, lower density (higher API), lower viscosity, lower residuum content, etc.) is described. The reactor is operable under continuous) semi-continuous or batch mode and is equipped with means to enable momentum, heat and mass transfer in and out of and within the reactor.

FIELD OF THE INVENTION

The present invention relates to upgrading of hydrocarbons, especiallyheavy hydrocarbons such as whole heavy oil, bitumen, and the like usingsupercritical water.

BACKGROUND OF THE INVENTION

Oil produced from a significant number of oil reserves around the worldis simply too heavy to flow under ambient conditions. This makes itchallenging to bring remote, heavy oil resources closer to the markets.One typical example is the Hamaca field in Venezuela. In order to rendersuch heavy oils flowable, one of the most common methods known in theart is to reduce the viscosity and density by mixing the heavy oil witha sufficient diluent. The diluent may be naphtha, or any other streamwith a significantly higher API gravity (i.e., much lower density) thanthe heavy oil.

For a case such as Hamaca, diluted crude oil is sent from the productionwellhead via pipeline to an upgrading facility. Two key operations occurat the upgrading facility: (1) the diluent stream is recovered andrecycled back to the production wellhead in a separate pipeline, and (2)the heavy oil is upgraded with suitable technology known in the art(coking, hydrocracking, hydrotreating, etc.) to produce higher-valueproducts for market. Some typical characteristics of these higher-valueproducts include lower sulfur content, lower metals content, lower totalacid number (TAN), lower residuum content, higher API gravity, and lowerviscosity. Most of these desirable characteristics are achieved byreacting the heavy oil with hydrogen gas at high temperatures andpressures in the presence of a catalyst. In the case of Hamaca, theupgraded crude is sent further to the end-users via tankers. Thesediluent addition/removal processes and hydrogen-addition or otherupgrading processes have a number of disadvantages:

1. The infrastructure required for the handling, recovery, and recycleof diluent could be expensive, especially over long distances. Diluentavailability is another potential issue.

2. Hydrogen-addition processes such as hydrotreating or hydrocrackingrequire significant investments in capital and infrastructure.

3. Hydrogen-addition processes also have high operating costs, sincehydrogen production costs are highly sensitive to natural gas prices.Some remote heavy oil reserves may not even have access to sufficientquantities of low-cost: natural gas to support a hydrogen plant. Thesehydrogen-addition processes also generally require expensive catalystsand resource intensive catalyst handling techniques, including catalystregeneration.

4. In some cases, the refineries and/or upgrading facilities that arelocated closest to the production site may have neither the capacity northe facilities to accept the heavy oil.

5. Coking is often used at refineries or upgrading facilities.Significant amounts of by-product solid coke are rejected during thecoking process, leading to lower liquid hydrocarbon yield. In addition,the liquid products from a coking plant often need furtherhydrotreating. Further, the volume of the product from the cokingprocess is significantly less than the volume of the feed crude oil.

A process according to the present invention overcomes thesedisadvantages by using supercritical water to upgrade a heavyhydrocarbon feedstock into an upgraded hydrocarbon product or syncrudewith highly desirable properties (low sulfur content, low metalscontent, lower density (higher API), lower viscosity, lower residuumcontent, etc.). The process neither requires external supply of hydrogennor must it use catalysts. Further, the process in the present inventiondoes not produce an appreciable coke by-product.

In comparison with the traditional processes for syncrude production,advantages that may be obtained by the practice of the present inventioninclude a high liquid hydrocarbon yield; no need for externally-suppliedhydrogen; no need to provide catalyst; significant increases in APIgravity in the upgraded hydrocarbon product; significant viscosityreduction in the upgraded hydrocarbon product; and significant reductionin sulfur, metals, nitrogen, TAN, and MCR (micro-carbon residue) in theupgraded hydrocarbon product.

Various methods of treating heavy hydrocarbons using supercritical waterare disclosed in the patent literature. Examples include U.S. Pat. Nos.3,948,754, 3,948,755, 3,960,706, 3,983,027, 3,988,238, 3,989,618,4,005,005, 4,151 068, 4,557,820, 4,559,127, 4,594,141, 4,840,725,5,611,915, 5,1914,031 and 6,887,369 and EP671454.

U.S. Pat. No. 4,840,725 discloses a process for conversion of highboiling liquid organic materials to lower boiling materials usingsupercritical water in a tubular continuous reactor. The water andhydrocarbon are separately preheated and mixed in a high-pressure feedpump just before being fed to the reactor.

U.S. Pat. No. 5,914,031 discloses a three zone reactor design so thatthe reactant activity, reactant solubility and phase separation ofproducts can be optimized separately by controlling temperature andpressure. However, all the examples given in the patent were obtainedusing batch operation.

U.S. Pat. No. 6,887,369 discloses a supercritical water pretreatmentprocess using hydrogen or carbon monoxide preferably carried out in adeep well reactor to hydrotreat and hydrocrack carbonaceous material.The deep well reactor is adapted from underground oil wells, andconsists of multiple, concentric tubes. The deep well reactor describedin the patent is operated by introducing feed streams in the core tubesand returning reactor effluent in the outer annular section.

Although the above-mentioned patents disclosed and claimed variousmethods and processes for heavy oil upgrading using supercritical water,such as operating range of temperature, and pressure, water to oilratio, etc, none has disclosed the design of the reactor or designrelated process controls for heavy oil upgrading using supercriticalwater. In fact, most of the examples disclosed in the patents wereobtained through batch tests using an autoclave. Although there arenumerous references to reactor design for processes involvingsupercritical water, most of them are for the application of wastetreatment and none of those references has addressed the design of areactor for both heavy oil and supercritical water, which isfundamentally different from processes of waste treatment usingsupercritical water, as discussed below.

It has long been known in the art that supercritical water can be usedfor waste treatment, especially for treating wastewater containingorganic contaminants. Therefore, there are numerous disclosures in theliterature on reactor design for waste treatment using supercriticalwater, tended to address the following issues:

-   -   (1) Solid handling. Waste streams typically contain both organic        and inorganic materials. Although organic materials can be        destroyed quickly through supercritical water oxidation,        inorganic materials are insoluble in supercritical water.        Several patents address this concern. For example, U.S. Pat.        Nos. 5,560,823 and 5,567,698 incorporated by reference herein        disclose a reversible flow reactor having two reaction zones        which are alternately used for supercritical water oxidation        while the remaining reaction zone is flushed with subcritical        effluent from the active reaction zone. U.S. Pat. No. 6,264,844,        incorporated by reference herein, discloses a tubular reactor        for supercritical water oxidation. The velocity of the reaction        mixture is sufficient to prevent settling of solid. Inorganic        salts in the effluent mixture, which are insoluble at conditions        of supercritical temperature and pressure for water, are        dissolved in a liquid water phase during cooling down of the        effluent mixture at an outlet end of the reactor.    -   (2) Oxidizer management. U.S. Pat. Nos. 5,384,051 and 5,558,783,        incorporated by reference herein, disclose a reactor design for        supercritical wastewater oxidation. It contains a reaction zone        inside the containment vessel and a permeable liner around the        reaction zone. An oxidizer is mixed with a carrier fluid such as        water. The mixture is heated and pressurized to supercritical        conditions, and then introduced to the reaction zone gradually        and uniformly by forcing it radially inward through the        permeable liner and toward the reaction zone. The permeable        liner permits the continuous, gradual, uniform dispersion of a        reactant and therefore promotes an even and efficient reaction.        The liner also isolates the pressure vessel from high        temperature and oxidizing conditions found in the reaction zone,        allowing a reduction in cost of the pressure vessel. EP 1489046        discloses a double-vessel design with a reaction vessel placed        inside a pressure vessel. Reaction takes place inside the        reactor vessel at high temperature, pressure and corrosive        environments. The outer pressure vessel will only see water.    -   (3) Containment of toxic material. Some waste stream contains        contaminants that are extremely harmful to humans and the        environment, therefore the possibility of releasing of such        harmful material has to be addressed in the reactor design. U.S.        Pat. No. 6,168,771, incorporated by reference herein, discloses        a reactor design including an autoclave inside a pressure        vessel. The pressure between autoclave and pressure vessel is        essentially equal to that inside the autoclave, therefore        eliminating possible leaking of toxic material inside the        autoclave.

Although heavy oil upgrading using supercritical water may be consideredsimilar in some respects to waste treatment using supercritical water,and can be implemented using various elements of reactors designed forwaste treatment, there are significant differences in requirement forreactor design for heavy hydrocarbon upgrading from that for wastetreatment. Specifically, the following are among the many issues to beaddressed in designing a reactor in which to conduct an effectiveprocess for heavy oil upgrading using supercritical water:

-   -   (1) Importance of selectivity. For waste treatment, the only        performance target is conversion. In other words, the reaction        is non-selective total oxidation and there is no need to worry        about selectivity, which makes the reactor design much easier.        For heavy oil upgrading, the feed is a mixture containing broad        range of materials, and the reactions involved are much more        complex. We need not only to consider conversion, but also more        importantly to pursue high selectivity, since non-selective        reactions will lead to low-value byproducts such as solid coke        or gases. Obviously, reactor design for selective reactions in a        complex system is very different and much more challenging than        that for non-selective total oxidation.    -   (2) High concentration of feed. Typically the organic component        concentration in the waste stream is low, and in many situations        the concentration is only in the ppm range. For oil upgrading,        it is preferable to run the reaction using the lowest possible        water to oil ratio to reduce capital and operating cost. The oil        concentration is typically several orders of magnitude higher in        upgrading as opposed to waste treatment.    -   (3) High density and viscosity One distinguishing feature of        heavy oil is high density and viscosity. In fact, this is one of        the primary reasons that the oil has to be upgraded. The density        of heavy oil is very close to liquid water, and viscosity can be        as high as 10,000 cp. High density and viscosity, together with        high concentration make the dispersion of heavy oil into        supercritical water an important consideration.

SUMMARY OF THE INVENTION

The present invention relates to an apparatus for upgrading ahydrocarbon by reaction with a fluid comprising water undersupercritical water conditions comprising; means for dispersing andmixing the fluid comprising water and the hydrocarbon under conditionswhich disfavor thermal cracking and formation of coke; means forinjecting a dispersed water-hydrocarbon mixture into a reaction zoneunder supercritical water conditions; a reaction zone having means formaintaining a uniform temperature within said reaction zone, means forcontrolling the residence time in the reaction zone within determinedlimits and means for avoiding the settling of inorganic solids withinthe reaction zone; and means for recovering an upgraded hydrocarbon.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process flow diagram of one embodiment of a processemploying an apparatus of the present invention.

FIG. 2 is a process flow diagram of another embodiment of a processemploying an apparatus of the present invention.

FIG. 3 is a process flow diagram of another embodiment of a processemploying an apparatus of the present invention.

FIG. 4 is a process flow diagram of another embodiment of a processemploying an apparatus of the present invention.

FIG. 5 is a process flow diagram of another embodiment of a processemploying an apparatus of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Reactants

Water and hydrocarbons, preferably heavy hydrocarbons are the tworeactants employed in a process according to the present invention.

Any hydrocarbon can be suitably upgraded by a process according to thepresent invention. Preferred are heavy hydrocarbons having an APIgravity of less than 20°. Among the preferred heavy hydrocarbons areheavy crude oil, heavy hydrocarbons extracted from tar sands, commonlycalled tar sand bitumen, such as Athabasca tar sand bitumen obtainedfrom Canada, heavy petroleum crude oils such as Venezuelan Orinoco heavyoil belt crudes Boscan heavy oil, heavy hydrocarbon fractions obtainedfrom crude petroleum oils particularly heavy vacuum gas oils, vacuumresiduum as well as petroleum tar, tar sands and coal tar. Otherexamples of heavy hydrocarbon feedstocks which can be used are oilshale, shale oil, and asphaltenes.

Water

Any source of water may be used in the fluid comprising water inpracticing the present invention. Sources of water include but are notlimited to drinking water, treated or untreated wastewater, river water,lake water, seawater, produced water or the like.

Mixing

In accordance with the invention, the heavy hydrocarbon feed and a fluidcomprising water that has been heated to a temperature higher than itscritical temperature are contacted in a mixing zone prior to enteringthe reaction zone. In accordance with the invention, mixing may beaccomplished in many ways and is preferably accomplished by a techniquethat does not employ mechanical moving parts. Such means of mixing mayinclude, but are not limited to, use of static mixers, spray nozzles,sonic or ultrasonic agitation, or thermal siphons.

The oil and water should be heated and mixed so that the combined streamwill reach supercritical conditions in the reaction zone.

It was found that by avoiding excessive heating of the feed oil, theformation of byproduct such as solid residues is reduced significantly.One aspect of this invention is to employ a heating sequence so that thetemperature and pressure of the hydrocarbons and water will reachsupercritical reaction conditions in a controlled manner. This willavoid excessive local heating of oil, which will lead to solid formationand lower quality product. In order to achieve better performance, theoil should only be heated up with sufficient amount of water present andaround the hydrocarbon molecules. This requirement can be met by mixingoil with water before heating.

In one embodiment of the present invention, water is heated to atemperature higher than its critical temperature, and then mixed withoil. The temperature of heavy oil feed should be kept in the range ofabout 100° C. to 200° C. to avoid thermal cracking but still high enoughto maintain a reasonable pressure drop. The water stream temperatureshould be high enough to make sure that after mixing with oil, thetemperature of the oil-water mixture is still higher than the watersupercritical temperature. In this embodiment, the oil is actuallyheated up by water. An abundance of water molecules surrounding thehydrocarbon molecules will significantly suppress condensation reactionsand therefore reduce formation of coke and solid product.

The required temperature of the supercritical water stream, T_(SCW), canbe estimated based on reaction temperature, T_(R), and water to oilratio. Since the heat capacity of water changes significantly in therange near its critical conditions, for a given reaction temperature,the required temperature for the supercritical water stream increasesalmost exponentially with decreasing water-to-oil ratio. The lower thewater-to-oil ratio, the higher the T_(SCW). The relationship, however,is very nonlinear since higher T_(SCW) leads to a lower heat capacity(far away from the critical point).

In another embodiment, water is heated up to supercritical conditions.Then the supercritical water mixed with heavy oil feed in a mixer. Thetemperature of heavy oil feed should be kept in the range of about 100°C. to 200° C. to avoid thermal cracking but still high enough tomaintain reasonable pressure drop. After mixing with heavy oil, thetemperature of the water-oil mixture would be lower than criticaltemperature of water; therefore a second heater is needed to raise thetemperature of the mixture stream to above the critical temperature ofwater. In this embodiment, the heavy oil is first partially heated up bywater, and then the water-oil mixture is heated to supercriticalconditions by the second heater.

Other methods of mixing and heating sequences based on the aboveteachings may be used to accomplish these objectives as will berecognized by those skilled in the art.

Reaction Conditions

After the reactants have been mixed, they are passed into a reactionzone in which they are allowed to react under temperature and pressureconditions of supercritical water, i.e. supercritical water conditions,in the absence of externally added hydrogen, for a residence timesufficient to allow upgrading reactions to occur. The reaction ispreferably allowed to occur in the absence of externally added catalystsor promoters, although the use of such catalysts and promoters ispermissible in accordance with the present invention.

“Hydrogen” as used herein in the phrase, “in the absence of externallyadded hydrogen” means hydrogen gas. This phrase is not intended toexclude all sources of hydrogen that are available as reactants. Othermolecules such as saturated hydrocarbons may act as a hydrogen sourceduring the reaction by donating hydrogen to other unsaturatedhydrocarbons. In addition, H₂ may be formed in-situ during the reactionthrough steam reforming of hydrocarbons and water-gas-shift reaction.

The reaction zone preferably comprises a reactor, which is equipped witha means for collecting the reaction products (syncrude, water, andgases), and a section, preferably at the bottom, where any metals orsolids (the “dreg stream”) may accumulate.

Supercritical water conditions include a temperature from 374° C. (thecritical temperature of water) to 1000° C., preferably from 374° C. to600° C. and most preferably from 374° C. to 400° C., a pressure from3,205 (the critical pressure of water) to 10,000 psia, preferably from3,205 psia to 7,200 psia and most preferably from 3,205 to 4,000 psia,an oil/water volume ratio from 1:0.1 to 1:10, preferably from 1:0.5 to1:3 and most preferably about 1:1 to 1:2.

The reactants are allowed to react under these conditions for asufficient time to allow upgrading reactions to occur. Preferably, theresidence time will be selected to allow the upgrading reactions tooccur selectively and to the fullest extent without having undesirableside reactions of coking or residue formation. Reactor residence timesmay be from 1 minute to 6 hours, preferably from 8 minutes to 2 hoursand most preferably from 20 to 40 minutes.

The Reactor

A reactor designed for heavy oil upgrading using supercritical water inaccordance with the present invention will preferably include thefollowing features:

The reactor will have means for adequate oil-water mixing anddispersion. Contrary to the conventional thermal cracking in anuncontrolled fashion that will lead to excessive formation of lighthydrocarbon and therefore lower liquid hydrocarbon yield at thetemperature and pressure under supercritical water conditions, heavyhydrocarbons will hydrothermally crack into lighter components.Furthermore, hydrocarbon radicals formed from thermal cracking will alsorecombine and polymerize and eventually become coke. Water molecules,especially under supercritical conditions, can quench and stabilizehydrocarbon radicals and therefore prevent them from over cracking andpolymerization. To avoid over cracking into light hydrocarbons and cokeformation, the heavy hydrocarbon molecules are preferably surrounded bywater molecules to the greatest practical extent. Therefore, the reactorincludes means to assure adequate mixing of oil with water for thepurpose of achieving a high yield of liquid hydrocarbons. Such meansshould be chosen so as to be able to handle heavy oil feed which has lowAPI gravity and high viscosity at high oil to water ratio. Depending onspecific applications such means can include, among others (a) nozzles;(b) static mixer; (c) stirring vessel; (d) micro-channel device; andsonic and ultrasonic device.

The reaction zone in accordance with the present invention willpreferably:

-   -   (1) Provide an appropriate residence time to achieve high        conversion and liquid yield. Controlling the residence time        narrowly within determined limits is a very important factor for        heavy oil upgrading using supercritical water. The desired        products of heavy oil upgrading are liquid hydrocarbons.        Insufficient residence time will lead to low conversion and        hence low liquid hydrocarbon yield. On the other hand, excess        conversion will lead to low value by products such as light        hydrocarbon gas and coke. In order to achieve highly selective        conversion to liquid hydrocarbons, it is critical to maintain        adequate residence time.    -   (2) Provide sufficient heat transfer rate to maintain uniform        temperature distribution. In comparing other supercritical water        applications, heavy oil is a much more complicated feed and        heavy oil upgrading is a very complex process. In addition, as        indicated above, the desired liquid hydrocarbon is an        intermediate product from selective, partial reaction.        Therefore, it is extremely important to control reaction        temperature to achieve high liquid hydrocarbon yield. Adequate        control of reaction temperature can be achieved by providing        enough heat transfer area, uniform feed distribution; or by        quenching.    -   (3) Be able to handle solid formed during the reaction. During        the reaction, small amounts of solid byproducts, primarily        inorganic materials (metals, sulfur, coke etc), will be formed,        and the reaction zone must be able to handle such solids so they        will not cause operating problems and will not contaminate the        liquid hydrocarbon product.

The present invention also employs a separation zone for productrecovery. The effluent stream from the reaction zone contains liquidhydrocarbon product, gas, water under supercritical conditions andsolids. The liquid hydrocarbons are generally separated from othercomponents to achieve high yield. The preferred way is to remove thesolid first, and then bring the fluid phase containing hydrocarbonproducts, supercritical water and gas byproducts out of supercriticalcondition by lowing temperature, pressure or both so that hydrocarbonproduct and water will condense into liquid phase. The solids areprimarily inorganic materials formed during the reactions and can beseparated from the supercritical fluid phase using separation techniquesknown in the art, which could be a disengaging zone in the reactor or aseparate device such as settling vessel, filter, cyclone etc.

Another option for separating the solids is to bring the product streamout of supercritical regime by lowing temperature or pressure or both.Then the solid will precipitate. A potential disadvantage of this optionis that some of the inorganic components in the solid may dissolve inwater, which may contaminate the liquid hydrocarbon product. It shouldbe noted that depending on the specific applications, a reactor forheavy oil upgrading using supercritical water in accordance with thepresent invention may have more than one of each of the three componentslisted above.

FIG. 1 shows an embodiment of the present invention, which has been usedin a laboratory. An inline mixer is used for mixing heavy oil withwater. For this specific embodiment it is a static mixer. The reactionzone comprises a spiral tube reactor with large length to diameter ratioto attain high velocity inside the reactor, which is helpful to maintainoil-water dispersion. This design also makes the fluid flow inside thereactor close to plug flow and therefore achieves narrow residence timedistribution for selective conversion to desired liquid hydrocarbons.Inorganic solids in the feed and formed during the reaction will notdissolve in supercritical water. High velocity inside the reactor alsoprevents settling of those inorganic solids. The small diameter of thereactor body also provides large specific surface area for heat transferto maintain uniform temperature distribution inside the reactor. Thelength of the reactor can be designed based on residence time needed forspecific conversion. A second vessel is added to settle the solids. Thetemperature and pressure is maintained at the same values as those inthe spiral tube so that the fluid in the second vessel is still atsupercritical water conditions. Due to the larger cross-sectional areaof the second vessel the fluid velocity is much lower. As a result,inorganic materials separated from the fluid will settle down in thevessel, and can be removed from the system. The fluid containinghydrocarbon products, supercritical water and gas byproducts is cooledwhile maintaining at the same pressure as in the reactor, andhydrocarbon products and water are condensed in the high pressureseparator.

A spiral tube with a high length to diameter ratio which may be from 50to 10,000, preferably from 100 to 4,000 may be used as reactor body. Useof such a reactor has the advantages of high velocity, narrow residencetime distribution, and large surface for heat transfer. The length todiameter ratio is a useful parameter to determine preferred reactorconfigurations. The diameter may be determined by velocity needed toavoid solids precipitation and then the length can be selected toprovide the desired residence time. Other reactor configurations knownto those in the art can be used to achieve similar effects such as aserpentine reactor.

In the embodiments shown in FIG. 1 the separation zone for removingsolid and recovering hydrocarbon products is a vessel with a dip tube.Other fluid solid separation devices known in the art can be used toachieve the separation effect, which includes, but not limited to,cyclone, filter, ceramic membrane, settling tank, etc.

In the embodiment shown in FIG. 1, as well as in other embodimentsdescribed herein, the mixer, reaction and separation zones areseparated. Such arrangement is convenient for laboratory research, andis used as an illustrative example. It is within the scope of thepresent invention and in some applications will be beneficial tointegrate these three functions into one vessel.

As mentioned above, the reactor may include more than one piece of eachfunction devices. FIG. 2 shows an example. In order to avoid overcracking of the feed to form undesired byproducts such as lighthydrocarbon gases and coke, heavy hydrocarbon molecules are preferablysurrounded by sufficient water molecules. Generally speaking, a higherwater to oil ratio will be helpful to maintain the desired environment.However, high water to oil ratio also means high equipment and operatingcost. The embodiment shown in FIG. 2 can achieve high water to oil ratiolocally without increasing overall water to feed ratio. Instead ofmixing all the feed oil with water at reactor inlet, this embodimentuses multiple injections of oil to maintain a desired water to oilratio. Such a design is also helpful to control reaction temperature. Bydistributing feed oil more uniformly through the reactor length,reaction temperature will not increase too much due to the exothermicnature of the reactions.

Only two injections were shown in FIG. 2 This is not intended as alimitation. A reactor with multiple injections may also be used. Inaddition, one or more settling vessels can be added to a reactor with amultiple injection configuration to achieve solid separation undersupercritical conditions.

FIG. 3 shows yet another embodiment with more than one mixing andreaction zones. A second mixer, which may or may not be the same as thefirst mixer, is added between reaction zone to enhance theoil/supercritical water mixing. Again, multiple mixers and reactionzones can be used. The upgrading reaction is exothermic. A reactor witha large surface area helps to maintain uniform temperature distributioninside the reactor.

Depending on feed properties; heat exchange through the surface areaprovided by the reactor may or may not be enough. Water can be used toquench the reaction stream and thereby control the reaction temperature.

FIG. 4 shows an embodiment of using water to quench the reaction streambetween two reaction zones. The amount of water used for quenchingshould be enough to bring down the reaction temperature while thereaction stream after quenching still maintain supercritical conditions.Multiple reaction zones and water quenching may be necessary for somefeeds.

The quenching water can also be used to for product recovery, as shownin FIG. 5. After reaction the product stream is quenched by liquidwater. The solid will be washed out by the water, and: due to thetemperature reduction caused by quenching water and the hydrocarbonswill condense as liquid.

Reaction Product Separation

After the reaction has progressed sufficiently, a single phase reactionproduct is withdrawn from the reaction zone, cooled, and separated intogas, effluent water, and upgraded hydrocarbon phases. This separation ispreferably done by cooling the stream and using ones or more two-phaseseparators, three-phase separators or other gas-oil-water separationdevice known in the art. However, any method of separation can be usedin accordance with the invention.

The composition of gaseous product obtained by treatment of the heavyhydrocarbons in accordance with the process of the present inventionwill depend on feed properties and typically comprises lighthydrocarbons, water vapor, acid gas (CO₂ and H₂S), methane and hydrogen.The effluent water may be used, reused or discarded. It may be recycledto e.g. the feed water tank, the feed water treatment system or to thereaction zone.

The upgraded hydrocarbon product, which is sometimes referred to as“syncrude” herein may be upgraded further or processed into otherhydrocarbon products using methods that are known in the hydrocarbonprocessing art.

The process of the present invention may be carried out either as acontinuous or semi-continuous process or a batch process or as acontinuous process. In the continuous process the entire system operateswith a feed stream of oil and a separate feed stream of supercriticalwater and reaches a steady state; whereby all the flow rates,temperatures, pressures, and composition of the inlet, outlet andrecycle streams do not vary appreciably with time.

While not being bound to any theory of operation, it is believed that anumber of upgrading reactions are occurring simultaneously at thesupercritical water conditions used in the present process. In apreferred embodiment of the invention the major chemical/upgradingreactions are believed to be:

Thermal Cracking: C_(x)H_(y)→lighter hydrocarbons

Steam Reforming: C_(x)H_(y)+2xH₂O=xCO₂+(2x+y/2)H₂

Water-Gas-Shift: CO+H₂O═CO₂+H₂

Demetalization: C_(x)H_(y)Ni_(w)+H₂O/H₂→NiO/Ni(OH)₂+lighter hydrocarbons

Desulfurization: C_(x)H_(y)S_(z)+H₂O/H₂=H₂S+lighter hydrocarbons

The exact pathway may depend on the reactor operating conditions(temperature, pressure, O/W volume ratio), reactor design (mode ofcontact/mixing, sequence of heating), and the hydrocarbon feedstock.

The following Examples are illustrative of the present invention, butare not intended to limit the invention in any way beyond what iscontained in the claims which follow.

EXAMPLE 1 Process Conditions

Oil and supercritical water are contacted in a mixer prior to enteringthe reactor. The reactor is equipped with air inner tube for collectingthe products (syncrude, excess water, and gas), and a bottom sectionwhere any metals or solids comprising a “dreg stream” of indeterminateproperties or composition may accumulate. The shell-side of the reactoris kept isothermal during the reaction with a clamshell furnace andtemperature controller. Preferred reactor residence times are 20-40minutes, with preferred oil/water volume ratios on the order of 1:3.Preferred temperatures are around 374°-400° C., with the pressure at3200-4000 psig. The reactor product stream leaves as a single phase, andis cooled and separated into gas, syncrude, and effluent water. Theeffluent water is recycled back to the reactor. Sulfur from the originalfeedstock accumulates in the dreg stream for the most part, with lesseramounts primarily in the form of H₂S found in the gas phase and waterphase.

As the next examples will show, very little gas is produced in mostcases. With suitable choice of operating conditions, it is also possibleto reduce or nearly eliminate the “dreg stream.” Elimination of the dregstream means that a greater degree of hydrocarbon is recovered assyncrude, but it also means that metals and sulfur will accumulateelsewhere, such as in the water and gas streams.

EXAMPLE 2 Properties of the Product Syncrude

A Hamaca crude oil was diluted with a diluent hydrocarbon at a ratio of5:1 (20 vol % of diluent:). The diluted Hamaca crude oil properties weremeasured before reacting it with the supercritical water process asreferred to in Example 1 and FIG. 2. The properties of the crude were asfollows, 12.8 API gravity at 60/60; 1329 CST viscosity @40° C.; 7.66 wt% C/H ratio, 13.04 wt % MCRT; 3.54 wt % sulfur; 0.56 wt % nitrogen, 3.05mg KOH/gm acid number; 1.41 wt % water; 371 ppm Vanadium; and 86 ppmNickel. The diluted Hamaca crude oil after the super critical watertreatment was converted into a syncrude with the following properties:24.1 API gravity at 60/60: 5.75 CST viscosity @40° C., 7.40 wt % C/Hratio; 2.25 wt % MCRT; 2.83 wt % sulfur; 0.28 wt % nitrogen; 1.54 mgKOH/gm acid number; 0.96 wt % water; 24 ppm. Vanadium; and 3 ppm Nickel.Substantial reductions in metals and residues were observed, withsimultaneous increase in the API gravity and a significant decrease inthe viscosity of the original crude oil feedstock. There were modestreductions in the Total Acid number, sulfur concentration, and nitrogenconcentration which could be improved with further optimization of thereaction conditions.

When the diluted Hamaca crude was sent directly to the reactor withoutbeing first heated with supercritical water, the product syncrude hadthe following properties; 14.0 API gravity at 60.60; 1:88 CST viscosity@40° C.; 8.7 wt % MCRT; 3.11 wt % sulfur; 267 ppm Vanadium; and 59 ppmNickel. This comparison demonstrates the, importance of the heatingsequence of the present invention.

Apart from the occasional, small accumulation of a: dreg stream, thereis very little coking or solid byproducts formed in the supercriticalwater reaction. The material balance was performed for two separateexperimental runs.

In the experimental run with no dreg stream formed, the startingfeedstock of diluted Hamaca crude at 60 grams produced a syncrudeproduct of 59.25 grams which corresponds to a high overall recovery of99 percent. It was thought that due to the absence of a dreg stream, theexperimental mass; balance was impacted in the determination of thesulfur and metals. The gas phase did not contain metals species and hadlittle sulfur compounds. It was hypothesized that a portion of the metaland sulfur may have accumulated on the walls of the reactor ordownstream plumbing.

In the experimental run with a dreg stream formed, the startingfeedstock of diluted Hamaca crude at 30 grams produced a syncrudeproduct of 22.73 grams. The dreg stream that was formed accounted for5.5 grams. The overall recovery with the dreg stream was 96.7 percent.In the dreg stream, sulfur accounted for 31% of the total sulfur withthe remaining sulfur in the oil product, water phase, and gas phase. Themetals content of the dreg stream accounted for 82% of the total metalswith the remaining metals in the oil product. For commercial operations,it may be preferable to minimize the formation of a dreg stream, sinceit represents a 18% reduction in syncrude product, and generates a lowervalue product stream that impacts the process in terms of economics anddisposal concerns.

Undiluted Boscan crude oil properties were measured before reacting itwith the supercritical water process of the present invention. Theproperties of the crude were as follows: 9 API gravity at 60/60; 1,140CST viscosity @40° C.; 8.0 wt % C/H ratio; 16 wt % MCRT; 5.8 wt %Sulfur;, and 1,280 ppm Vanadium;. The undiluted Boscan crude oil afterthe super critical water treatiment was converted into a syncrude withthe following properties: 22 API: gravity at 60/60; 9 CST viscosity @40°C.; 7.6 wt % C/H ratio, 2.5 wt % MCRT; 4.6% sulfur; and 130 ppmVanadium.

A simulated distillation analysis of the original crude oil vs. thesyncrude products from different experimental runs shows that thesyncrude prepared in accordance with the present invention clearly hassuperior properties than the original crude. Specifically, the syncrudescontain a higher fraction of lower-boiling fractions, 51% of the dilutedHamaca crude boils across a range of temperatures of less than 1000° F.,while employing a process according to the present invention usingsupercritical water depending on process configurations, between 79 to94% of the synrcrude boils across a range of temperatures of less than1000° F. 40% of the undiluted Boscan crude boils across a range oftemperatures of less than 1000° F., while employing a process accordingto the present invention using supercritical water, 93% of the syncrudeboils across a range of temperatures of less than 1000° F.

There are numerous variations on the present invention which arepossible in light of the teachings and supporting examples describedherein. It is therefore understood that within the scope Of thefollowing claims, the invention may be practiced otherwise than asspecifically described or exemplified herein.

1. An apparatus for upgrading a hydrocarbon by reaction with a fluidcomprising water under supercritical water conditions comprising: a.means for dispersing and mixing the fluid comprising water and thehydrocarbon under conditions which disfavor thermal cracking andformation of coke. b. means for injecting a dispersed water-hydrocarbonmixture into is a reaction zone under supercritical water conditions; c.a reaction zone having means for maintaining a uniform temperaturewithin said reaction zone; means for controlling the residence time inthe reaction zone within determined limits and means for avoiding thesettling of inorganic solids within the reaction zone; and d. means forrecovering an upgraded hydrocarbon.
 2. An apparatus according to claim1, wherein the means for dispersing the fluid comprising water and thehydrocarbon comprise at least one static mixer, spray nozzle, sonic orultrasonic agitator, thermal siphon or combinations thereof
 3. Anapparatus according to claim 1, wherein the reaction zone comprises areactor having means for collecting reaction products and means foraccumulating metals or solids.
 4. An apparatus according to claim 1wherein the means for recovering an upgraded hydrocarbon comprises avessel having a dip tube a cyclone, a filter, a membrane or a packedbed.
 5. An apparatus according to claim 1, wherein the reaction zonecomprises a tubular reactor having a length to diameter ratio from 50 to10,000 and a length selected to provide adequate residence time in thereaction zone.
 6. An apparatus according to claim 1, wherein thereaction zone comprises a tubular reactor having a length to diameterratio from 100 to 4,000 and a length selected to provide adequateresidence time in the reaction zone.
 7. An apparatus according to claim1 wherein the reaction zone compresses a tubular reactor having adiameter selected to sustain a turbulent flow of reactants to avoidprecipitation of solids and a length selected to provide adequateresidence time in the reaction zone.
 8. An apparatus according to claim1, wherein the reaction zone comprises at least two reactors.
 9. Anapparatus according to claim 8 further comprising quenching meansbetween said at least two reactors.
 10. An apparatus according to claim3, wherein a mixer precedes the reactor.